1. Because the chemical properties of gold powder are not stable enough, it is assumed that when contacted with acids, alkalis, carbon and sulfides, chemical changes will occur to varying degrees, which will greatly reduce the metallic luster of gold powder and make gold ink appear black. Therefore, golden ink should be avoided for printing large areas of domestic copperplate paper and offset paper. Because the paper consumed by acid paper making process is acidic, golden ink will not only discolor after printing, but also lose luster. In the same way, the distribution of auxiliary materials of golden ink should not use acid-containing auxiliary materials, but should adopt neutral material distribution.
2. Because the gold ink is easy to contact with air and water vapor and cause discoloration due to chemical reactions, it is necessary to do a good job in the storage of gold powder, do not let it be exposed to the air at will, and the unused gold powder should be wrapped tightly and tightly.
3. The application of metals should be controlled according to the principle of adjusting with printing, that is, the one-time allotment should be suitable for continuous printing for about 3 hours, so as to avoid excessive adjustments of gold powder in grease for too long and losing its golden luster due to oxidative transformation in contact with air.
4. The speed of golden ink printing should not be too fast. Because the speed of the machine is too fast, the friction heat of the roller increases correspondingly, which makes the golden ink oxidized and blackened easily. Therefore, the printing speed should be controlled at about 3000 sheets per hour.
5. Alcohols or gums should be used in the embossing solution of offset printing gold, so as not to make the ink dark and lose luster because of the reaction between acid embossing solution and gold powder.
6. Cots should be adjusted properly when printing gold, and the positions of COTS should be adjusted accurately so as to avoid the occurrence of ink piling in the process of printing due to poor ink transmission, so that gold powder can stay on the cots for a long time and cause oxidative discoloration of gold ink. In addition, the number of rollers used for gold printing should be used as little as possible to reduce the chance of gold blackening caused by friction heat.
7. When the machine ink bucket and ink roller have just been cleaned with kerosene and gas oil, the organic solvent remaining on the surface of the machine has not been completely volatilized, that is to say, the printing of gold ink will be stopped immediately, which will cause the reaction between the gold ink and the solvent to cause discoloration.
8. Don't stack too many semi-wastes of printing gold ink. Assuming that too much heat released by printing gold ink in the monotonous process of paper surface can't be distributed as soon as possible, it will also make the gold ink oxidized and discolored.
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